1. Field of the Invention
The invention relates to a steering system that includes a variable transmission ratio mechanism that is able to vary a transmission ratio between a steering angle and a steered angle.
2. Description of the Related Art
A technique of this type is described, for example, in Japanese Patent Application Publication No. 11-301507 (JP-A-11-301507). JP-A-11-301507 describes a vehicle steering limiting device. The vehicle steering limiting device includes a limiting mechanism that limits operation of a variable transmission ratio mechanism on the basis of a steering angle and a steered angle.
Incidentally, the variable transmission ratio mechanism, for example, includes a reduction mechanism, such as a planetary gear mechanism, and a motor coupled to a gear of the reduction mechanism, and controls the magnitude of current supplied to the motor to control the transmission ratio. Here, it is conceivable that feedback (FB) control is executed in order to increase the accuracy of control over the variable transmission ratio mechanism. However, when feedback control, such as PID control in which the rate of contribution of I operation is relatively large, is executed, redundant current is supplied to the motor during operation of the limiting mechanism, and there is a possibility that it is difficult to efficiently control the variable transmission ratio mechanism.